I am planning a new bathroom for our basement. The basement is currently unfinished. When the house was built, the stubs were installed for a bathroom in the basement. However, we need to make the bathroom handicapped accessible and want to change the arrangement. The attached sketch shows what we have now and what we are planning.

My apologies for the primitive sketch. The top of the sketch is a side view of the existing stubs and the bottom view is a plan view. The room is 10â€™6â€ x 10â€™6â€ and each light square is 6â€x6â€. The black lines show mostly the existing and planned walls, floor and framing. The red shows the existing plumbing. I know the approximate run for the 4â€ line under the slab but not the 2â€ lines. The blue (drain) and green (vent) show what I am thinking is required to service the new tub, shower, lav and toilet. I plan to remove/cap the existing stubs when bust open the floor slab. Hopefully this conveys what I am thinking. Basically I want to tie the new 4â€ line into the existing stub and provide a vent via the drain for the new lav. The shower and tub drain into the existing 4 â€œ drain line. I think the shower and tub are too far removed and require their own vent. Both new vents would feed into the existing vent line. All old vent and drain stubs would be removed.

â€¢ Will this work and comply with most codes?
â€¢ Is there a better way to do this?
â€¢ Anything in particular that is tricky beyond what is shown?

I would reconsider the tub and shower drains and vents. The shower is flowing past the tub, which is unvented.

Not sure what your plan is for that space between the tub and the shower? If there are walls there, vents for both fixtures would have a place to come up and could be combined in the overhead.

Less important, but you could save a bit of work and material by eliminating the unnecessary bends in the WC drain and the lav drain. Straight runs are always better. Also, the WC drain only need be 3".

I do not know the existing condition of the room, but if I had free latitude to do it anyway I wanted to, that is not how I would do it. But it depends on how "deep" the existing is and how much concrete can be cut as to whether your idea is a good one or not. The tub is being wet vented by the shower's vent, which is acceptable for that application.

I do not know the existing condition of the room, but if I had free latitude to do it anyway I wanted to, that is not how I would do it. But it depends on how "deep" the existing is and how much concrete can be cut as to whether your idea is a good one or not. The tub is being wet vented by the shower's vent, which is acceptable for that application.

Click to expand...

Right now the basement is totally unfinished and open so, other than the rough-ins, I have freedom to change things up a fair amount. I am eager for suggestions to improve the design. I ran a snake and magnet down the 4 in drain and located its run. I also measured that the top of the 4 in drain line is 9 inches below the top of the concrete slab - fairly deep? I am not sure of the routing nor tie-ins for the existing rough-ins for the tub/shower and lav drains - I assume that will become apparent when I start busting through the concrete slab. My interior decorator and lead designer (i.e., wife) likes the overall arrangement of the bathroom design. Other than that, I'm interested in how to improve the plumbing design - and I need all the help I can get!

Great advice to minimze the unnecessary bends - were you thinking to take the WC drain at 45 angle from the WC straight to a 45 into the existing 4 in drain line? Should I just run 3 in from the WC elbow and into a 4 in x 3 in wye at the existing 4 in line?

Not sure I understand the comment about the unvented tub - I have attempted to satisfy vent requirements for the shower and tub by having a vertical vent that is located midway between them that ties into the existing vent line - will that not satisfy vent requirements for both of these fixtures?

The planned shower is a freestanding glass surround. My plan was to only have a tile covered box or knee wall at the end of the tub to contain the drain but nothing more or higher.

I would reconsider the tub and shower drains and vents. The shower is flowing past the tub, which is unvented.

Not sure what your plan is for that space between the tub and the shower? If there are walls there, vents for both fixtures would have a place to come up and could be combined in the overhead.

Less important, but you could save a bit of work and material by eliminating the unnecessary bends in the WC drain and the lav drain. Straight runs are always better. Also, the WC drain only need be 3".

Great advice to minimze the unnecessary bends - were you thinking to take the WC drain at 45 angle from the WC straight to a 45 into the existing 4 in drain line? Should I just run 3 in from the WC elbow and into a 4 in x 3 in wye at the existing 4 in line?

Not sure I understand the comment about the unvented tub - I have attempted to satisfy vent requirements for the shower and tub by having a vertical vent that is located midway between them that ties into the existing vent line - will that not satisfy vent requirements for both of these fixtures?

The planned shower is a freestanding glass surround. My plan was to only have a tile covered box or knee wall at the end of the tub to contain the drain but nothing more or higher.

Click to expand...

Your plan makes proper venting very problematic. HJ has a lifetime of experience with this that I do not. I would present your plan to the local plumbing inspector. He is the one you need to make happy.

Your plan makes proper venting very problematic. HJ has a lifetime of experience with this that I do not. I would present your plan to the local plumbing inspector. He is the one you need to make happy.

Click to expand...

THANKS for the feedback. Could the vent issue between the tub and shower be resolved by bringing both drains to a common point below the vent and then running the drain out from there (assuming the inspector doesn't like the idea of a wet vent)?

The vent being between the tub and shower, does NOT make it a vent for the tub, but your inspector would probably allow it to wet vent the tub.

Click to expand...

THANKS HJ. Any other suggestions or comments?

I am going to be out your way in May - going up to Jerome - ever been to the junkyard there? Definitely worth the visit - incredible collection of junk from restored gasoline tankers to mining equipment to cars to you name it!